<!DOCTYPE html>
<html>
<head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title></title>
	<style type="text/css">
		*{
			margin: 0;
			padding: 0;
		}
/*		.g-content{
			position: absolute;
			left: 0;
			right: 0;
			top: 0;
			bottom: 0;
			width: 200px;
			height: 200px;
			margin: auto;
			background: red;
		}
		*/
		.g-content{
			position: absolute;
			left: 50%;
			top: 50%;
			width: 200px;
			height: 200px;
			margin-left: -100px;
			margin-top: -100px;
		
			background: red;
		}
		
	</style>
</head>
<body>

<div class='g-content'></div>

</body>
</html>